A core drill is used to extract the core samples of the earth for analysis by a geologist. The core drill is typically composed of a number of drill pipes which are connected end to end to form a drill string. An outer barrel assembly is attached to a downhole end of the drill string and includes a core bit for drilling the core sample. An inner core barrel assembly is run down the drill string and releasably latched inside the outer barrel assembly. The unit core barrel assembly includes a head assembly, a swivel, and an inner core barrel. The swivel attaches the head assembly to the inner core barrel in a manner which rotationally decouples the inner core barrel from the drill string. Therefore as the drill string rotates the inner core tube assembly is rotationally stationary and receives the core sample being cut by the drill bit.
The core orientation system is provided in the inner core barrel assembly. The core orientation system logs or records the in situ orientation of the core sample. This is used by the geologist to enable accurate mapping of geology and mineralogy of the earth. The core orientation system may be housed or attached at various locations within the inner core barrel assembly. However it is important for the core orientation system to have a fixed and known rotational relationship with the inner core tube.
An inner core barrel assembly usually also includes a check valve downhole of the spindle. The purpose of the check valve is to allow fluid and in particular liquid to pass through the inside of the inner core tube and then to the outside of the head assembly when the inner core barrel assembly is being run down the drill string for releasable locking to the outer core barrel assembly. Allowing this flow and subsequent bypass of fluid reduces the time taken for the inner core barrel assembly to which the inner core barrel assembly. Given that the drill holes can be of a debt substantially greater than I km and filled with water or drilling mud the descent time can be substantial. Reducing the descent time enables more meters to be drilled per day and thereby decreases operational costs. A common check valve has a ball valve, a ball seat and one or more openings or bypass passages spaced from the seat. When the inner core barrel assembly descends through liquid, the liquid pass up the inner core tube, forces the ball valve off the seat and flows out of the inner core tube through the openings or bypass passages. Once the inner core barrel assembly has landed fluid pressure can be provided from the surface which now flows through the openings/bypass passages and forces the valve ball onto the valve seat. Thereafter the fluid pressure can act on the inner core barrel assembly to achieve various effects or operate subsystems within the assembly.
The above references to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the application of the apparatus, systems, devices and methods as disclosed herein.